This was a study to look at changes in markers of bone turnover in young women who were classified by amount of physical activity and who had a variety of luteal phase defects. The following markers of bone turnover were assayed in the Core Lab: bone alkaline phosphatase, osteocalcin, free deoxypyridinioline crosslinks, crosslinked N-telopeptides of type I collagen. Urine and serum collected at 4 time points in 30 women were assayed (480 samples). Data analysis is currently underway. A manuscript should be completed within the next month.